1. Field of the Invention
The present invention relates to injection molding machines and, more particularly, to a mechanically openable and closable safety gate for the die closing unit of an injection molding machine which has a drive-reversing safety mechanism with a pivotable contact member on its leading edge for the protection of the machine operator.
2. Description of the Prior Art
Industrial safety codes require that all injection molding machines have safety covers or safety gates which prevent access to the clamping space of the injection molding die, when the machine is in operation. The use of a mechanically closable safety gate brings with it the additional requirement of protecting the operator or mechanic against injury, when the cover is executing its closing movement.
U.S. Pat. No. 4,382,764 discloses such a drive-reversing mechanism for the motor-driven safety gate of an injection molding machine, the rectangular safety gate carrying a contact ledge pivotably attached to its leading edge. The pivot connection is formed by an interior fold corner of the channel-shaped contact ledge engaging an exterior corner of smaller angle at the junction of the main panel and the front side flange of the safety gate, a corner-adjoining positioning flange of the contact ledge being yieldingly clamped to the main panel of the safety gate by means of holding pins and compression springs.
An end flange of the contact ledge, reaching behind the free edge of the safety gate side flange, carries a switch-actuating member which moves perpendicularly against the contact plunger of an electrical switch, when the contact ledge is pivoted rearwardly, as the result of encountering an obstacle in its closing path. During the resultant rearward movement of the actuating member, a cam portion on the leading edge of the actuator member produces a depression of the switch plunger, the remaining flat portion of the actuating member maintaining the switch plunger in the depressed state, as the contact ledge and its actuating member continue their rearward movement.
The axis of the switch plunger being parallel to the pivot axis of the contact ledge, this mechanism requires a precise positioning of the contact ledge in relation to the safety gate along the pivot axis, as any shifting of the contact ledge along this line will affect the interaction between the actuating member and the switch plunger in terms of changing the level to which the latter is depressed.